TBO I wouldn't have upgraded to an 1100T CPU over what you have now as the differences might turn out to be minimal, depending on your usage and needs.

So I think it would've perhaps been a better choice to do a few other things.
Such as updating your motherboard BIOS and then try your hand at overclocking your current CPU to get a little more out of it.

But overall, buying an SSD and reinstalling your OS fresh would also be a very good way to refresh the system and it should then be alot more responsive and that in itself should prolong the system a bit.

Instead of upgrading the CPU, I would've invested more into a newer/faster GPU that you could then carry over to a newer system down the road.

Since you have DDR2, yes upgrading down the road will mean new motherboard, CPU and RAM.

Now if you were to upgrade to some sort of AM3+ motherboard, you can still use your AM3 1100T CPU on it, and then use DDR3 RAM.

The real world differences between DDR2 and DDR3 though are very slim and for most part aren't even noticeable in everyday tasks. DDR3's design though does allow for higher clocks, lower timings, and lower voltages. Depending on the DDR3 RAM you buy and what all the motherboard supports and how flexible it's capabilities are.

Yes, the difference between SATA II/III in terms of real speed only really comes into play when you're comparing SSDs. Even then, SATA II SSDs are fairly quick and the difference over ANY mechanical drive and an older SATA II SSD is huge.

So what should I buy?
Edit: I feel like the 1100T would do be some good, cause I tend to try and run 2-3 copies of minecraft at a time, and it doesn't work very well... I can run 2 copies and League of Legends fine, but everything else is horrible.

I would start with the Crucial M4 listed for you. Get it up and running on the current hardware and gauge performance once you do that. Then decide how far you want to take the upgrade afterward. One of the nice things about the SSD is that it really isn't dependent on the other hardware as much like Memory, CPU, Motherboard, GPU, and PSU.

You have to have a SATA mobo that supports AHCI. That's pretty much it. I bought that exact drive and I'm running it on a SATA II motherboard and it's fast as lightning. I can only imagine what it will be like after I get SATA III.

You have to have a SATA mobo that supports AHCI. That's pretty much it. I bought that exact drive and I'm running it on a SATA II motherboard and it's fast as lightning. I can only imagine what it will be like after I get SATA III.

You probably won't notice the difference that much, unless you run benchies.